The mammalian circadian clock drives and maintains 24-h rhythms in physiology and integrates multiple signals into a phase change consistent with the environment. The research goal of this proposal is to investigate neuropeptide communication underlying this integration within the primary, mammalian circadian pacemaker, the suprachiasmatic nucleus (SCN). The long-term goal is to provide essential training that will facilitate the transition of the grantee from a mentored postdoctoral research position to an independent, tenure-track faculty position. Under the direction of the sponsor, the mentored phase will investigate the ionic basis for neurophysiological changes induced by the peptide, gastrin-releasing peptide (GRP), during intra- SCN photic transduction. This phase will also provide the time and mentoring necessary for a faculty job search and critical training in patch clamp electrophysiology that will be used to establish a model paradigm for the experiments outlined in the research plan. In order to investigate how the circadian network within the SCN interprets conflicting phase shifting stimuli, real-time clock gene imaging, pharmacological and electrophysiological endpoints will be combined to explore the interaction of photic and nonphotic stimuli and the subsequent changes in neurophysiology and molecular rhythms using a unique animal model (Per1::GFP) that allows examination of neurophysiological properties of individual, living, Pert-expressing cells. Specifically, I will use Per7::GFP and PER2::LUC mice to: (1) determine the phase dependence and transduction mechanisms for concurrent photic and nonphotic entraining stimuli, (2) investigate the neural circuitry and neurophysiology associated with GRP-mediated photic transduction during the day, and (3) determine whether the neurophysiological and molecular effects of the nonphotic transmitter, neuropeptide Y (NPY), vary across the circadian cycle. The proposed research plan will substantially contribute to the long- term goal of establishing a successful independent research program studying circadian neurophysiology and behavior. The results of these studies have implications for human health, including circadian rhythm disruptions associating with mood disorders and shift work. RELEVANCE: This research plan will investigate how the brain's biological clock integrates light and nonphotic resetting environmental stimuli (e.g. stress, exercise, etc) when present simultaneously. The results of these studies will have implications for jet lag/shift work, circadian rhythm disorders, as well as treatment developments for circadian disruptions in those suffering from mood and developmental disorders.